In many Northwestern European countries the stone was formerly used for trade, with a value ranging from about 5 to 40 local pounds (3 to 15 kg). With the advent of metrication from the mid-19th century on, it was superseded by the kilogram. It remained in limited use for trade in the United Kingdom and in Ireland until prohibited by the Weights and Measures Act of 1985.[4][5]

The name "stone" derives from the use of stones for weights – a practice that dates back into antiquity. The ancient Hebrew Law against the carrying of "diverse weights, a large and a small"[6] is more literally translated as "you shall not carry a stone and a stone (אבן ואבן), a large and a small". There was no "standard" stone in the ancient Jewish world,[7] but in Roman times weights crafted to a multiple of the Roman libra (a pound of about 327.54 g) for use in commerce were often made of stone.[8] Such weights varied in quality – 10 and 50 [Roman] pound examples acquired in Italy, possibly from Pompeii, were of polished blackstone,[9] while a 40 pound example on exhibition in Eschborn, close to the Roman frontier in Germany, was made of sandstone.[10]

During the Middle Ages, a conveniently-sized rock was often chosen as a local standard for weighing agricultural commodities, but the weight of such rocks varied with the commodity and region. By the late Middle Ages, international trade, such as England's exports of raw wool to Florence, required a fixed standard and, in 1389, a royal statute of Edward III fixed the stone of wool at 14 pounds.[11]

In England, potatoes were traditionally sold in stone and half-stone (14 pounds and 7 pounds, respectively) increments, but the Oxford English Dictionary contains examples including the following:[12]

STONE also denotes a certain quantity or weight of some commodities. A stone of beef, in London, is the quantity of eight pounds; in Hertfordshire, twelve pounds; in Scotland sixteen pounds.

In 1661, the Royal Commission of Scotland recommended that the Troy stone be used as a standard of weight and that it be kept in the custody of the burgh of Lanark. The Scots stone was equal to 16 Scots pounds (17 lb 8 oz avoirdupois or 7.936 kg). The tron (or local) stone of Edinburgh, also standardised in 1661, was 16 tron pounds (24 lb 1 oz avoirdupois or 9.996 kg).[14][15] In 1789, an encyclopedic enumeration of measurements was printed for the use of "his Majesty's Sheriffs and Stewards Depute, and Justices of Peace, ... and to the Magistrates of the Royal Boroughs of Scotland" and provided a county-by-county and commodity-by-commodity breakdown of values and conversions for the stone and other measures.[16] The Scots stone ceased to be used for trade when the Act of 1824 established a uniform system of measure across the whole of the United Kingdom, which at that time included all of Ireland.[17]

Ireland used the pound avoirdupois: before the early nineteenth century, as in England, the stone varied both with locality and with commodity (e.g., the Belfast stone for measuring flax equaled 16.75 pounds[18]) with the most usual value being 14 pounds.[19] Among the oddities related to the use of the stone was the practice in County Clare of a stone of potatoes being 16 lb in the summer and 18 lb in the winter.[19]

Traditionally, live animals were weighed in stones of 14 lb; but, once slaughtered, their carcases were weighed in stones of 8 lb. Thus, if the animal's carcase accounted for 8⁄14 of the animal's weight, the butcher could return the dressed carcases to the animal's owner stone for stone, keeping the offal, blood and hide as his due for slaughtering and dressing the animal.[21] The 8 lb stone continued to be used for meat at Smithfield market until shortly before the Second World War.[22]

The Weights and Measures Act of 1824, which applied to all of the United Kingdom, consolidated the weights and measures legislation of several centuries into a single document. It revoked the provision that bales of wool should be made up of 20 stones, each of 14 pounds, but made no provision for the continued use of the stone. Ten years later, a stone still varied from 5 pounds (glass) to 8 pounds (meat and fish) to 14 pounds (wool and "horseman's weight").[23] However, the Act of 1835 permitted a stone of 14 pounds to be used for trade[24] but other values continued to be used – Britten, in 1880 for example, catalogued a number of different values of the stone in various British towns and cities ranging from 4 lb to 26 lb.[25] The value of the stone and associated units of measure that were legalised for purposes of trade were clarified by the Weights and Measures Act 1835 as follows:[24]

Pounds

Unit

Stone

kg

1

1 pound

1⁄14

0.4536

14

1 stone

1

6.350

28

1 quarter

2

12.70

112

1 hundredweight

8

50.80

2240

1 (long) ton

160

1016

The use of the stone in the British Empire was varied. In Canada for example, it never had a legal status.[26] Shortly after the United States declared independence, Thomas Jefferson, then Secretary of State presented a report on weights and measures to the U.S. House of Representatives. Even though all the weights and measures in use in the United States at the time were derived from English weights and measures, his report made no mention of the stone being used. He did, however, propose a decimal system of weights in which his "[decimal] pound" would have been 9.375 ounces (265.8 g) and the "[decimal] stone" would have been 5.8595 pounds (2.6578 kg).[27]

In 1965, the then Federation of British Industry informed the British Government that its members favoured the adoption of the metric system. The Board of Trade, on behalf of the Government, agreed to support a ten-year metrication programme. There would be minimal legislation, as the programme was to be voluntary and costs were to be borne where they fell.[28] Under the guidance of the Metrication Board, the agricultural product markets achieved a voluntary switchover by 1976.[29] The stone was not included in the Directive 80/181/EEC as a unit of measure that could be used within the EEC for "economic, public health, public safety or administrative purposes",[30] though its use as a "supplementary unit" was permitted. The scope of the directive was extended to include all aspects of the EU internal market as from 1 January 2010.[30]

With the adoption of metric units by the agricultural sector, the stone was, in practice, no longer used for trade; and, in the Weights and Measures Act 1985, passed in compliance with EU directive 80/181/EEC,[30] the stone was removed from the list of units permitted for trade in the United Kingdom.[31] In 1983, in response to the same directive, similar legislation was passed in Ireland.[32] The Act repealed earlier acts that defined the stone as a unit of measure for trade.[31] (British law had previously been silent regarding other uses of the stone.)

The stone remains widely used in Britain and Ireland for human body weight: in those countries people may commonly be said to weigh, e.g., "11 stone 4" (11 stones and 4 pounds), rather than "72 kilograms" as in many other countries, or "158 pounds" (the conventional way of expressing the same weight in the United States). The correct plural form of stone in this context is stone (as in, "11 stone" or "12 stone 6 pounds"); in other contexts, the correct plural is stones (as in, "Please enter your weight in stones and pounds"). In Australia and New Zealand, metrication has almost entirely displaced stone and pounds since the 1970s.[citation needed]

In many sports in both Britain and Ireland, such as professional boxing, wrestling and horse racing,[33] the stone is used to express body weights.

Before the advent of metrication, units called "stone" (German: Stein; Dutch: steen; Polish: kamień) were used in many North-Western European countries.[34][35] Its value, usually between 3 and 10 kg, varied from city to city and sometimes from commodity to commodity. The number of local "pounds" in a stone also varied from city to city. During the early 19th century, states such as the Netherlands (including Belgium) and the South Western German states, which had redefined their system of measures using the kilogramme des Archives as a reference for weight (mass), also redefined their stone to align it with the kilogram.

This table shows a selection of stones from various North European Continental cities:

Although the advent of the metric system spelt the demise of the stone as a unit of measure, the stone was used in some early discussions and implementations of the metric system. In his Philosophical essay written in 1668, John Wilkins proposed a system of measure whose unit of length, the standard, was approximately one metre and whose unit of mass was the mass of a cubic standard of rainwater (which would have been approximately 1,000 kg). He proposed that one tenth of this mass (100 kg) should be called a stone.[38][39] In 1791, a few years before the French Revolutionary Government agreed on the metre as the basis of the metric system, Thomas Jefferson, in a report to Congress proposed that the United States should adopt a decimal currency system (which was adopted) and a decimal-based system of measure (which was not adopted).[40] Jefferson's proposal for units of measure included a "decimal" pound equal to 9.375 ounces (265.8 g) in the "customary" system and a "decimal" stone of 10 "decimal" pounds or 5.8595 pounds (2.6578 kg).

Neither Wilkins' nor Jefferson's proposals were adopted; but, in the Netherlands, where the metric system was adopted in 1817, the pond (pound) was set equal to a kilogram.[nb 2] and the steen (stone), which had previously been 8 Amsterdam pond (3.953 kg), was redefined as being 3 kg.[35]